BrickworX web server builds RNA and DNA models into electron density maps at resolutions as low as 4 &Aring.
On input the program requires a MTZ file with structure factor amplitudes and phases. Optionally, the user may provide phosphate group

phosphorus atom positions (predicted internally by default).
On output Brickworx provides two files in PDB format; the predicted phosphorus atom pattern (if applicable) and a model in a full-atom representation.